Field of the Invention
The present invention relates to a calibration apparatus and a calibration method.
Description of the Related Art
The image quality of today's display apparatuses is becoming higher and higher, as well as the demands of the users for the stability and high-precision color reproduction of the display devices.
However, color reproduction by a display apparatus changes due to, for example, the time-related deterioration of the display elements thereof. Calibration of the display apparatus on a regular basis is therefore necessary in order to always realize stable color reproductivity.
Japanese Patent Application Laid-open No. 2002-209230 and Japanese Patent Application Laid-open No. 2007-208629, for example, disclose the conventional calibration techniques.
According to the technique disclosed in Japanese Patent Application Laid-open No. 2002-209230, a patch image is displayed on the screen of a display apparatus. Then, the quality of the displayed image (the image displayed on the screen) is adjusted based on the display brightness (the brightness on the screen) and display color (the color on the screen) of the patch image which a user measured using an optical sensor.
According to the technique disclosed in Japanese Patent Application Laid-open No. 2007-208629, a plurality of patch images are displayed on the screen of a display apparatus at the same time. Then, an image of the screen (the plurality of patch images) is captured by an imaging apparatus such as a digital camera, and the image quality of the displayed image is adjusted based on the result of capturing the plurality of patch images. According to the technique disclosed in Japanese Patent Application Laid-open No. 2007-208629, because the measurement values of the plurality of patch images can be acquired at once, calibration can be executed within a short period of time.
However, as a result of simultaneously displaying the plurality of patch images on the screen, the light emitted from the patch image A is reflected off the surrounding wall or the like of the display apparatus and irradiated onto the region of the patch image B. As a result, the display brightness or display color of the patch image B are changed by the light emitted from the patch image A and reflected off the surrounding wall or the like of the display apparatus, lowering the calibration accuracy. Specifically, the calibration accuracy drops because calibration is executed based on the measurement value of the patch image B that is impacted by the reflected light.
The impacts of the reflected light are now described with reference to FIG. 9.
FIG. 9 illustrates an example in which four patch images are displayed simultaneously on the screen of a display apparatus. Reference numeral 401 represents the display apparatus, reference numeral 402 the patch images, and reference numeral 403 an imaging apparatus.
As shown in FIG. 9, let it assume that the plurality of patch images 402 of high brightness to low brightness are displayed simultaneously on the screen of the display apparatus 401. In this case, as shown by the arrow in FIG. 9, the light from the high-brightness patch image is reflected off a surrounding wall of the display apparatus 401 (a wall of the room where the display apparatus 401 is placed), and this reflected light is irradiated onto the low-brightness patch image. As a result, the display brightness of the low-brightness patch image is enhanced by the reflected light, changing the measurement value of the low-brightness patch image.
Furthermore, when the plurality of patch images 402, including a patch image C of a first color and a patch image D of a second color that is different significantly from the first color, are displayed simultaneously on the screen, the light from the patch image C is reflected off a surrounding wall of the display apparatus 401, and this reflected light is irradiated onto the patch image D. As a result, the display color of the patch image D is made close to the first color due to the reflected light, changing the measurement value of the patch image D.
The patch image, under the effect of the reflected light, is captured by the imaging apparatus 403, and calibration is executed based on this image-capturing result under the effect of the reflected light, lowering the calibration accuracy.